As is known, people suffering from certain pathological conditions, such as carpal tunnel syndrome (CTS), have an impaired sensitivity to vibration. The prior art provides devices for detecting such conditions by testing the patient's ability to sense vibration in a body extremity, such as a finger or a hand.
For example, U.S. Pat. No. 4,175,546, issued to Goldblatt et al., discloses a complex device for measuring sensitivity to externally applied vibration. The device includes a pallometer having a head or tool which is mounted on an end of a balance lever that is supported by a knife edge. The knife edge is mounted beneath a table having a upright opening through which an operative tip of the head projects. A counterweight mounted on the beam urges the head upwardly to lightly engage a stop with the operative tip exposed. When the tip is engaged by a patient, the head can swing downwardly so that the pressure of the tip on the patient is constant regardless of the pressure the patient may exert on the table at the edges of the opening.
U.S. Pat. No. 4,641,661, issued to Kalarickal, discloses an electronic algesimeter adapted to determine, by cutaneous sensation, the threshold of pain experienced by a patient at any skin site on the body. The instrument includes a pointed probe and is used by an examiner who continuously increases the pressure applied by the probe point on the skin until the patient feels the stimulus, at which critical point the pressure indication is then held. Since the instrument provides a real-time continuous readout, the muscular coordination of the examiner is not a factor.
U.S. Pat. No. 5,002,065, issued to LaCourse et al., discloses a vibratory screening or diagnostic system for diagnosing a patient to measure sensory disturbances of the patient. The system includes a vibratory stimulator for applying controlled and compensated vibratory forces to a finger, or other body portion, of the patient and a drive mechanism connected to effect vibration of the vibratory stimulator and operable to automatically effect discrete, but variable, vibrations at many frequencies over a wide range of frequencies and at variable amplitude levels at each frequency. The system also includes a response mechanism which permits the patient to record the onset of sensing by the patient of vibrations at each vibratory frequency.
The vibratory screening system of the LaCourse patent teaches a rather complex electrical and mechanical structure which requires a substantial amount of input information, such as the temperature of the fingertip skin, the pressure applied by the patient to the device and the wrist angle during testing, to function as described. Such a system is not only very costly, but is prone to diagnostic inaccuracies, since the results are based on many variables.